1. Field of the Invention
The present invention relates to an x-ray CT solid-state detector, and more particularly to an x-ray CT solid-state detector arranged such that fan-shape x-rays transmitted through a subject to be tested are detected, through a collimator device, by a number of radiation detector elements disposed in the form of an array.
2. Description of the Related Art
As generally shown in FIG. 15, a prior art x-ray CT apparatus comprises an x-ray CT solid-state detector comprising an x-ray tube 71, a collimator device 72 and detector blocks 73, and is arranged such that transmitted x-rays obtained by irradiating a fan-shape x-ray beam 75 from the x-ray tube 71 onto a subject to be tested, are guided to and detected by the detector blocks 73 through the collimator device 72.
In each of the detector blocks 73, combinations of scintillators for converting radiations into lights and photoelectric conversion elements for converting the lights into electric signals, are disposed in parallel on a substrate in the form of a one-dimensional array. In each block 73, 8 to 30 combinations of scintillators and photoelectric conversion elements are generally disposed on the substrate. Such detector blocks 73 are consecutively disposed in the form of a polygon on a predetermined circle and combined with the collimator device 72, thus forming the x-ray CT solid-state detector 74.
In such an x-ray CT solid-state detector, the collimator device 72 and each detector block 73 are secured to an attachment plate 80, as shown in FIG. 16. The collimator device 72 comprises a number of collimator plates 72a incorporated in a case-like support body (not shown in FIG. 16). Each of the collimator plates 72a is fixed to the attachment plate 80 through the support body such that each collimator plate 72a is directed to the point for generating x-rays. In each of the detector blocks 73, an assembly of a scintillator array 73a and a photodiode array 73b is fixed to a support stand 81. Each of the detector blocks 73 is fixed to the attachment plate 80 such that each detector block 73 and the collimator device 72 are made in a unitary structure. Each of the collimator plates 72a is required to be positioned A on each boundary B between adjacent scintillator elements. Accordingly, positioning pins 82 are disposed at the attachment plate 80. By fitting the pins 82 in fitting holes formed in the support stand 81 of the detector block 73, the collimator device 72 and each detector block 73 are positioned with respect to each other.
In such a prior art solid-state detector, the relative positional relationship between the collimator device 72 and the detector blocks 73 is determined only by the positioning pins 82. This disadvantageously makes it difficult to improve the positional precision. More specifically, the collimator plates 72a are held by the support body, and the scintillator arrays 73a are held by the support stands 81, and the support body and the support stands 81 are coupled through the attachment plates 80 and the pins 82. Thus, a number of members are interposed between the collimator plates 72a and the scintillator arrays 73a. This disadvantageously makes it difficult to improve the most important positional precision between the collimator plates 72a and the scintillator arrays 73a.